Flame retardant fiber blends comprising modacrylic fibers and fabrics and garments made therefrom

ABSTRACT

An intimate blend of staple fibers has from 10 to 75 parts by weight of at least one aramid staple fiber, from 15 to 80 parts by weight of at least one modacrylic staple fiber, and from 5 to 30 parts by weight of at least one polyamide staple fiber. The intimate blend of staple fibers provides yarns and fabrics that are flame retardant, also referred to as fire resistant, and can be used to make flame retardant articles, such as clothing. The flame retardant fabrics may have a basis weight from 4 to 15 ounces per square yard.

BACKGROUND OF THE INVENTION

There is an ongoing need for flame retardant, also referred to as fireresistant, fabrics that can be used to make clothing suitable for peoplewho work near flames, high temperatures, or electric arc flashes. Inaddition to showing excellent thermal performance, an effective flameretardant fabric should be durable, comfortable, and produced at lowcost. Although fabrics made of inherently flame retardant fibers havebeen very useful in protective garments, certain characteristics ofthese fibers present problems. For instance, these fibers can bedifficult to dye, provide uncomfortable fabric textures, and areexpensive. To address these problems, inherently flame retardant fibershave been blended with fibers made of other materials. Fiber blendingcan be used to obtain an end fabric that combines the beneficialcharacteristics of each of the constituent fibers. However, suchblending often comes at the expense of durability and thermalperformance.

Certain fiber blends and fabrics made from those blends are known in theart. For instance, U.S. Pat. No.4,920,000 (Green) issued on Apr. 24,1990 discloses a durable heat resistant fabric comprising certain blendsof cotton, nylon, and heat resistant fibers. U.S. Pat. No. 4,970,111(Smith, Jr.) issued Nov. 13, 1990 discloses a fire resistant fabriccomprising a blend of chlorine-containing polymeric fibers,polyacrylonitrile fibers, and a fire retarding polyester binder. U.S.Pat. No. 5,503,916 (Ichibori et al.) issued Apr. 2, 1996 discloses flameretardant clothing comprising natural or chemical fibers and a polymerfiber containing antimony and halogen compounds. U.S. Pat. No. 6,132,476(Lunsford et al.) issued Oct. 17, 2000 discloses dyed fabric blendscontaining inherently flame retardant fibers and flame retardantcellulosic fibers containing a flame retardant compound. U.S. Pat. No.6,254,988 B1 (Zhu et al.) issued on Jul. 3, 2001 discloses a fabriccomposed of particular blends of cotton, nylon, and para-aramid fibersthat is comfortable, cut resistant, and abrasion resistant. U.S. patentapplication Publication No. 2001/0009832 A1 (Shaffer et al.) publishedon Jul. 26, 2001 discloses a flame retardant fabric comprisingdissimilar warp and fill yarns wherein the warp yarns comprise staple orfilament fibers and have a Limiting Oxygen Index of at least 27, thefill yarns comprise natural fibers, and the ratio of warp to fill yarnends in the fabric is at least 1.0. U.S. Pat. No.6,547,835 B1 (Lunsfordet al.) issued on Apr. 15, 2003 discloses a method for dyeing flameretardant fabrics.

Fabrics made from the fiber blends and yarns discussed above eithernaturally suffer from poor resistance to abrasion or, as disclosed inU.S. Pat. No. 4,920,000 (Green) issued on Apr. 24, 1990, utilize a largepercentage of cotton fiber, which has very low abrasion resistance. Fireprotective clothing and garments are normally used in harsh environmentsso any improvement in abrasion resistance of the fabrics used in thosegarments is important and desired. There is therefore, a need for flameretardant fiber blends, yarns, and fabrics that have improved abrasionresistance.

SUMMARY OF THE INVENTION

In accordance with the purpose of the invention, as embodied and broadlydescribed herein, the invention is an intimate blend of staple fiberscomprising 10 to 75 parts by weight of at least one aramid staple fiber,15 to 80 parts by weight of at least one modacrylic staple fiber, and 5to 30 parts by weight of at least one polyamide staple fiber.

In another embodiment, the invention is an intimate blend of staplefibers comprising 20 to 40 parts by weight of at least one aramid staplefiber, 50 to 80 parts by weight of at least one modacrylic staple fiber,and 15 to 20 parts by weight of at least one polyamide staple fiber.

In another embodiment, the invention is one of the intimate blendsdescribed above, wherein the at least one aramid staple fiber ispoly(metaphenylene isophthalamide) and the at least one modacrylicstaple fiber is a copolymer of acrylonitrile and vinylidene chloride.

The modacrylic staple fiber of this invention preferably contains anantimony additive. The preferred antimony additive is an antimony oxide.

The intimate blends of this invention may be used to make a yarn, whichin turn may be used to make a flame retardant fabric for use in flameretardant articles such as clothing.

Further scope of applicability of the present invention will becomeapparent from the detailed description given hereinafter. However, itshould be understood that the detailed description and specificexamples, while indicating embodiments of the invention, are given byway of illustration only, because various changes and modificationswithin the spirit and scope of the invention will become apparent tothose skilled in the art from this detailed description. It is to beunderstood that both the foregoing general description and the followingdetailed description are exemplary and explanatory only and are notrestrictive of the invention, as claimed.

DETAILED DESCRIPTION

There is an ongoing need for fiber blends from which flame retardant,also referred to as fire resistant, fabrics can be made that can be usedto make clothing and other articles suitable for people who work nearflames, high temperatures, or electric arc flashes, and the like.Considerable effort has been made to increase the effectiveness of suchfiber blends and the resulting fabrics, while maintaining or improvingtheir comfort and durability and reducing their overall cost. Thepresent invention represents just such an advance in the field of flameretardant garments.

An intimate blend of staple fibers of this invention comprises aramidfibers, modacrylic fibers, and polyamide fibers. The proportions of eachcomponent are important to achieve the necessary combination of physicalqualities. By “intimate blend” is meant that two or more fiber classesare blended prior to spinning a yarn. In the present invention, theintimate blend is formed by combining aramid fibers, modacrylic fibers,and polyamide fibers in the fiber form, and then spinning into a singlestrand of yarn. By “yarn” is meant an assemblage of fibers spun ortwisted together to form a continuous strand, which can be used inweaving, knitting, braiding, or plaiting, or otherwise made into atextile material or fabric. Such yarns can be made by conventionalmethods for spinning staple fibers into yarns, such as, for example,ring-spinning, or higher speed air spinning techniques such as Murataair-jet spinning where air is used to twist the staple into a yarn.

The intimate blend of staple fibers of this invention includes aramidfibers, which are inherently flame retardant. By “aramid fiber” is meantone or more fibers made from one or more aromatic polyamides, wherein atleast 85% of the amide (—CONH—) linkages are attached directly to twoaromatic rings. Aromatic polyamides are formed by reactions of aromaticdiacid chlorides with aromatic diamines to produce amide linkages in anamide solvent. Aramid fibers may be spun by dry or wet spinning usingany number of processes, however, U.S. Pat. Nos. 3,063,966; 3,227,793;3,287,324; 3,414,645; 3,869,430; 3,869,429; 3,767,756; and 5,667,743 areillustrative of useful spinning processes for making fibers that couldbe used in this invention.

Aramid fibers are typically available in two distinct classes, namelymeta-aramid fibers, or m-aramid fibers, one of which is composed ofpoly(metaphenylene isophthalamide), which is also referred to as MPD-I,and para-aramid fibers, or p-aramid fibers, one of which is composed ofpoly(paraphenylene terephthalamide), also referred to as PPD-T.Meta-aramid fibers are currently available from E. I. du Pont de Nemoursof Wilmington, Del. in several forms under the trademark NOMEX®: NOMEXT-450® is 100% meta-aramid; NOMEX T-455® is a blend of 95% NOMEX® and 5%KEVLAR® (para-aramid); and NOMEX IIIA® (also known as NOMEX T-462®) is93% NOMEX®, 5% KEVLAR®, and 2% carbon core nylon. In addition,meta-aramid fibers are available under the trademarks CONEX® and APYEILOwhich are produced by Teijin, Ltd. of Tokyo, Japan and Unitika, Ltd. ofOsaka, Japan, respectively. Para-aramid fibers are currently availableunder the trademarks KEVLAR® from E.I. du Pont de Nemours of Wilmington,Del. and TWARON® from Teijin Ltd. of Tokyo, Japan. For the purposesherein, TECHNORA® fiber, which is available from Teijin Ltd. of Tokyo,Japan, and is made from copoly(p-phenylene/3,4′diphenyl esterterephthalamide), is considered a para-aramid fiber.

In one embodiment of this invention, the at least one aramid staplefiber is poly(metaphenylene isophthalamide).

The intimate blend of staple fibers of this invention also includesmodacrylic fibers. Modacrylic fibers are manufactured fibers in whichthe fiberforming substance is any long chain synthetic polymer composedof less than 85%, but at least 35%, by weight of acrylonitrile(—CH₂CH[CN]—)_(x), units. Modacrylic fibers are made from resins thatare copolymers (combinations) of acrylonitrile and halogen-containingcompounds, such as vinyl chloride, vinylidene chloride or vinyl bromide.Modacrylic fibers are inherently flame retardant because they arecopolymerized with these other compounds such as vinyl chloride,vinylidene chloride, or vinyl bromide. Modacrylic fibers arecommercially available under various trademarks, such as Protex®(ACN/polyvinylidene chloride co-polymer), which is available from KanekaCorporation of Osaka, Japan.

In one embodiment of this invention, the at least one modacrylic fiberis a copolymer of acrylonitrile and vinylidene chloride.

The modacrylic staple fibers of this invention preferably contain anantimony additive. The preferred antimony additive is an antimony oxide,preferably added in an amount greater than two percent by weight.

The intimate blend of staple fibers of this invention also includespolyamide fibers. By “polyamide fibers” is meant one or more fibers madefrom one or more aliphatic polyamide polymers, generically referred toas nylon. Examples include polyhexamethylene adipamide (nylon 66),polycaprolactam (nylon 6), polybutyrolactam (nylon 4),poly(9-aminononanoic acid) (nylon 9), polyenantholactam (nylon 7),polycapryllactam (nylon 8), and polyhexamethylene sebacamide (nylon 6,10). Nylon fibers are generally spun by extrusion of a melt of thepolymer through a capillary into a gaseous congealing medium. When nylonis the polyamide fiber in the intimate blend of staple fibers forming ayarn, such yarn preferably is used as the warp yarn when forming afabric to enhance protection against soft surface abrasion in thefinished fabric or garment made from such fabric. In one embodiment ofthis invention, when nylon is used in this manner to make the fabrics orgarments of this invention, the fabrics or garments of this inventionare expected to have more than ten percent higher resistance to abrasioncompared to similar fabrics without nylon, as measured in cycles tofailure according to the Abrasion Resistance Test described below.However, too much nylon in a fabric will cause the fabric to becomestiff and lose drape when the fabric is exposed briefly to hightemperatures.

In one embodiment of this invention, nylon fiber has a linear densityfrom 1 to 3 dtex. In another embodiment the nylon fiber has a lineardensity from 1 to 1.5 dtex. In yet another embodiment the nylon fiberhas a linear density of about 1.1 dtex.

The intimate blend of staple fibers of this invention can be used tomake yarns and fabrics that are flame retardant. These yarns and fabricscan be used to make flame retardant articles, such as flame retardantgarments and clothing, which are particularly useful for firefightersand other workers who are put in close proximity to flames, hightemperatures, or electric arc flashes. Generally, by “flame retardant”is meant that the fabric does not support flame in air after coming incontact with a flame for a short period of time. More precisely, “flameretardant” can be defined in terms of the Vertical Flame Test, describedbelow. Flame retardant fabrics preferably have a char length of lessthan six inches after a twelve second exposure to a flame. The terms“flame retardant,” “flame resistant,” “fire retardant,” and “fireresistant” are used interchangeably in the industry, and references to“flame retardant” compounds, fibers, yarns, fabric, and garments in thepresent invention could be described identically as “flame resistant,”“fire retardant,” or “fire resistant.” Staple fibers for use in spinningyarns are generally of a particular length and of a particular lineardensity. For use in this invention, synthetic fiber staple lengths of2.5 to 15 centimeters (1 to 6 inches) and as long as 25 centimeters (10inches) can be used, and lengths of 3.8 to 11.4 centimeters (1.5 to 4.5inches) are preferred. Yarns made from such fibers having staple lengthsof less than 2.5 centimeters have been found to require excessively highlevels of twist to maintain strength for processing. Yarns made fromsuch fibers having staple lengths of more than 15 centimeters are moredifficult to make due to the tendency for long staple fibers to becomeentangled and broken, resulting in short fibers. The synthetic staplefibers can be crimped or not, as desired for any particular purpose. Thestaple fibers of this invention are generally made by cutting continuousfilaments to certain predetermined lengths. However, staple fibers canbe made by other means, such as by stretch-breaking, and yarns can bemade from such fibers as well as from a variety or distribution ofdifferent staple fiber lengths.

In one embodiment of this invention, the yarn of this invention can beused to make a flame retardant fabric, which is a cloth produced byweaving, knitting, or otherwise combining the yarn of this invention.Flame retardant fabrics can be constructed having warp yarn comprisingthe yarns of this invention, fill yarn comprising the yarns of thisinvention, or both warp and fill yarns comprising the yarns of thisinvention. When fabrics use the yarn of this invention in only onedirection (i.e., as only fill or only warp), other suitable yarns may beused in the other direction according to the desired fabriccharacteristics. For best abrasion resistance, the yarn of thisinvention is used in the warp direction since warp yarn typically formsmost of the direct contact surface of a fabric. This translates intobetter abrasion performance of the outer surface of the fabric ingarment form.

In one embodiment of this invention, the flame retardant fabric has abasis weight of from 4 and 15 ounces per square yard. In anotherembodiment of this invention the flame retardant fabric has a basisweight of from 5.5 to 11 ounces per square yard. Such fabrics can bemade into articles of clothing, such as shirts, pants, coveralls,aprons, jacket, or any other single or multi-layer form for flash fireor electric arc protection.

The articles of the invention will be further described below withreference to the working examples. It should be noted however that theconcept of the invention will not be limited at all by these examples.

Test Methods

The following test methods were used in the following Examples.

Thermal Protective Performance Test (TPP). The predicted protectiveperformance of a fabric in heat and flame was measured using the“Thermal Protective Performance Test” (NFPA 2112). A flame was directedat a section of fabric mounted in a horizontal position at a specifiedheat flux (typically 84 kW/m²). The test measures the transmitted heatenergy from the source through the specimen using a copper slugcalorimeter with no space between the fabric and heat source. The testendpoint was characterized by the time required to attain a predictedsecond-degree skin burn injury using a simplified model developed byStoll & Chianta, “Transactions New York Academy Science”, 1971, 33 p649. The value assigned to a specimen in this test, denoted as the “TPPvalue,” is the total heat energy required to attain the endpoint, or thedirect heat source exposure time to the predicted burn injury multipliedby the incident heat flux. Higher TPP values denote better insulationperformance.

Vertical Flame Test. The “Vertical Flame Test” (ASTM D6413) is generallyused as a screening test to determine whether a fabric burns, as apredictor for whether an article of clothing has any flame retardingproperties. According to the test, a 3×12 inch section of fabric wasmounted vertically and a specified flame was applied to its lower edgefor twelve seconds. The response of the fabric to the flame exposure wasrecorded. The length of the fabric that was burned or charred wasmeasured. Times for afterflame (i.e., the continued burning of thefabric section after removing the test flame) and afterglow(characterized by smoldering of the fabric section after removing thetest flame) were also measured. Additionally, observations regardingmelting and dripping from the fabric section were recorded. Pass/failspecifications based on this method are known for industrial workerclothing, firefighter turnout gear and flame retardant station wear, andmilitary clothing. According to industry standards, a fabric can beconsidered flame retardant, or fire resistant, if it has a char lengthof less than six inches after a twelve second exposure to a flame.

Abrasion Resistance Test. Abrasion resistance was determined using ASTMmethod D3884, with a H-18 wheel, 500 gms load on a Taber abrasionresistance meter available from Teledyne Taber, 455 Bryant St., NorthTonawanda, N.Y. 14120. Taber abrasion resistance was reported as cyclesto failure.

Tear Strength Test. The tear strength measurement is based on ASTM D5587. The tear strength of textile fabrics was measured by the trapezoidprocedure using a recording constant-rate-of-extension-type (CRE)tensile testing machine. Tear strength, as measured in this test method,requires that the tear be initiated before testing. The specimen wasslit at the center of the smallest base of the trapezoid to start thetear. The nonparallel sides of the marked trapezoid were clamped inparallel jaws of a tensile testing machine. The separation of the jawswas increased continuously to apply a force to propagate the tear acrossthe specimen. At the same time, the force developed was recorded. Theforce to continue the tear was calculated from autographic chartrecorders or microprocessor data collection systems. Two calculationsfor trapezoid tearing strength were provided: the single-peak force andthe average of five highest peak forces. For the examples here, thesingle-peak force was used.

Grab Strength Test. The grab strength measurement, which is adetermination of breaking strength and elongation of fabric or othersheet materials, is based on ASTM D5034. A 100 mm (4.0 in.) widespecimen was mounted centrally in clamps of a tensile testing machineand a force applied until the specimen broke. Values for the breakingforce and the elongation of the test specimen were obtained from machinescales or a computer interfaced with testing machine.

EXAMPLES

Example 1 is a fabric of this invention comprising an intimate blend ofthis invention for both the warp and fill yarns. Example 2 is a fabricof this invention comprising an intimate blend of this invention for thewarp yarn and an intimate blend of aramid and modacrylic, for the fillyarn. Comparative Example A is not a fabric of this invention, butinstead comprises an intimate blend of aramid and modacrylic, with nonylon, for both the warp and fill yarns. Following are more detaileddescriptions of these examples, followed by test results for eachexample.

Example 1

A comfortable and durable fabric was prepared with warp and fill ringspun yarns comprising an intimate blend of Nomex® type 462, modacrylic,and nylon. Nomex® type 462 is 93% poly(m-phenyleneisophthalamide)(MPD-I), 5% poly(p-phenylene terephthalamide)(PPD-T) and2% static dissipative fibers (Type P-140, available from E. I. du Pontde Nemours of Wilmington, Del.). The modacrylic fibers in this examplewere ACN/polyvinylidene chloride co-polymer (available under thetrademark Protex®, from Kaneka Corporation of Osaka, Japan), and thenylon used was polyhexamethylene adipamide.

A picker blend sliver of 35 weight percent of Nomex® type 462, 50 weightpercent of the modacrylic and 15 weight percent of the nylon wasprepared and processed by the conventional cotton system into a spunyarn having twist multiplier of 3.7 using a ring spinning frame. Theyarn so made was a 24.6 tex (24 cotton count) single yarn. Two singleyarns were then plied on a plying machine to make a two-ply yarn for useas a warp yarn. Using a similar process and the same twist and blendratio, a 32.8 tex (18 cotton count) single yarn was made and then two ofthese yarns were plied for use as a fill yarn.

The Nomex®/modacrylic/nylon yarns were used as the warp and fill in ashuttle loom in a 3×1 twill construction. The greige twill fabric had aconstruction of 24 ends×15 picks per cm (60 ends×39 picks per inch), andbasis weight of 271.3 g/m² (8 oz/yd²). The greige twill fabric preparedas described above was scoured in hot water and dried under low tension.The scoured fabric was then dyed using acid dye. The finished fabric wasthen tested for its thermal and mechanical properties. The results ofthese tests are shown in Table 1.

Example 2

A comfortable and durable fabric was prepared comprising ring spun warpyarns made from an intimate blend of Nomex® type 462, modacrylic, andnylon, and ring spun fill yarns made from intimate blends of Nomex® type462 and modacrylic.

Nomex® type 462 is 93% poly(m-phenylene isophthalamide)(MPD-I), 5%poly(p-phenylene terephthalamide)(PPD-T) and 2% static dissipativefibers (Type P-140, available from E. I. du Pont de Nemours ofWilmington, Del.). The modacrylic in this example was ACN/polyvinylidenechloride co-polymer (available under the trademark Protex®, from KanekaCorporation of Osaka, Japan), and the nylon used was polyhexamethyleneadipamide.

A picker blend sliver of 35 weight percent of Nomex® type 462, 50 weightpercent of the modacrylic and 15 weight percent of the nylon wasprepared and processed by the conventional cotton system into a spunyarn having twist multiplier of 3.7 using a ring spinning frame. Theyarn so made was a 24.6 tex (24 cotton count) single yarn. Two singleyarns were then plied on a plying machine to make a two-ply yarn for useas a warp yarn. Using a similar process and the same twist, a 32.8 tex(18 cotton count) single yarn with a blend of 50 weight percent Nomex®type 462 and 50 weight percent of the modacrylic was made and then twoof these single yarns were plied for use as a fill yarn.

The Nomex®/modacrylic/nylon yarn was used as the warp and theNomex®/modaxrylic yarn was used as the fill in a shuttle loom in a 3×1twill construction. The greige twill fabric had a construction of 23ends×16 picks per cm (58 ends×40 picks per inch), and basis weight of264.5 g/m² (7.8 oz/yd²). The greige twill fabric prepared as describedabove was scoured in hot water and dried under low tension. The scouredfabric was then dyed using acid dye. The finished fabric was then testedfor its thermal and mechanical properties. The results of these testsare shown in Table 1.

Comparative Example A

A comfortable and durable fabric was prepared comprising ring spun warpyarns made from an intimate blend of Nomex® type 462 and modacrylic andring spun fill yarns made from an intimate blend of Nomex® type 462 andmodacrylic.

Nomex® type 462 is 93% poly(m-phenylene isophthalamide)(MPD-I), 5%poly(p-phenylene terephthalamide)(PPD-T) and 2% static dissipativefibers (Type P-140, available from E. I. du Pont de Nemours ofWilmington, Del.). The modacrylic in this example was ACN/polyvinylidenechloride co-polymer (available under the trademark Protex® from KanekaCorporation of Osaka, Japan).

A picker blend sliver of 50 weight percent of Nomex® type 462 and 50weight percent of the modacrylic was prepared and processed by theconventional cotton system into a spun yarn having twist multiplier of3.7 using a ring spinning frame. The yarn so made was a 24.6 tex (24cotton count) single yarn. Two of these single yarns were then plied ona plying machine to make a two-ply yarn for use as a warp yarn. Using asimilar process and the same twist, a 32.8 tex (18 cotton count) singleyarn with a blend of 50 weight percent Nomex® type 462 and 50 weightpercent of the modacrylic was made and then two of these single yarnswere plied for use as a fill yarn.

The Nomex®/modacrylic yarn was used as the warp and the fill in ashuttle loom in a 3×1 twill construction. The greige twill fabric had aconstruction of 23 ends×15 picks per cm (58 ends×38 picks per inch), andbasis weight of 254 g/m² (7.5 oz/yd²). The greige twill fabric preparedas described above was scoured in hot water and dried under low tension.The scoured fabric was then dyed using acid dye. The finished fabric wasthen tested by its thermal and mechanical properties. The results ofthese tests are shown in Table 1. TABLE 1 Example Test ResultsComparative Example No. Example 1 Example 2 Example A Fabric WarpNOMEX ®/ NOMEX ®/ NOMEX ®/ Design Yarn Protex ®/Nylon Protex ®/NylonProtex ® 35/50/15% by 35/50/15% by 50/50% by Weight Weight Weight FillNOMEX ®/ NOMEX ® NOMEX ®/ Yarn Protex ®/Nylon Protex ® Protex ® 35/50/15by 50/50% 50/50% by Weight by Weight Weight Test Description Value ValueValue Basis Weight  8 7.8 7.5 (oz/y²) Yarn Size 24/2 × 18/2 24/2 × 18/224/2 × 18/2 (count-warpxfill) TPP (cal/cm²) 12.9 13.5 14.9 VerticalFlame 3.8 × 3.6 3.6 ×4.1 2.3 × 2.6 Char (inch-warpxfill) Abrasion(Cycle) 752 651 452 Tear Resistance 43 × 40 41 × 36 42 × 39(lbf-warpxfill) Grab Strength 170 × 161 177 × 150 181 × 164(lbf-warpxfill)

1. An intimate blend of staple fibers, comprising: 10 to 75 parts byweight of at least one aramid staple fiber, 15 to 80 parts by weight ofat least one modacrylic staple fiber, and 5 to 30 parts by weight of atleast one polyamide staple fiber.
 2. The intimate blend of claim 1,wherein the at least one modacrylic staple fiber further comprises anantimony compound.
 3. The intimate blend of claim 1, wherein there are20 to 40 parts by weight of the at least one aramid staple fiber, 50 to80 parts by weight of the at least one modacrylic staple fiber, and 15to 20 parts by weight of the at least one polyamide staple fiber.
 4. Theintimate blend of claim 1, wherein the at least one aramid staple fiberis selected from the group consisting of para-aramid fibers, meta-aramidfibers, and mixtures thereof.
 5. The intimate blend of claim 3, whereinthe at least one aramid staple fiber is selected from the groupconsisting of para-aramid fibers, meta-aramid fibers, and mixturesthereof.
 6. The intimate blend of claim 1, wherein the at least onearamid staple fiber is poly(metaphenylene isophthalamide) and the atleast one modacrylic fiber is a copolymer of acrylonitrile andvinylidene chloride.
 7. The intimate blend of claim 3, wherein the atleast one aramid staple fiber is poly(metaphenylene isophthalamide) andthe at least one modacrylic fiber is a copolymer of acrylonitrile andvinylidene chloride.
 8. A yarn comprising the intimate blend of claim 1.9. A flame retardant fabric comprising the yarn of claim
 8. 10. Theflame retardant fabric of claim 9, wherein the flame retardant fabrichas a basis weight of from 4 to 15 ounces per square yard.
 11. A flameretardant article of clothing comprising the flame retardant fabric ofclaim
 10. 12. The flame retardant fabric of claim 9, wherein the flameretardant fabric has a basis weight of from 5.5 to 11 ounces per squareyard.
 13. A flame retardant article of clothing comprising the flameretardant fabric of claim
 12. 14. A yarn comprising the intimate blendof claim
 6. 15. A flame retardant fabric comprising the yarn of claim14.
 16. The flame retardant fabric of claim 15, wherein the flameretardant fabric has a basis weight of from 4 to 15 ounces per squareyard.
 17. A flame retardant article of clothing comprising the flameretardant fabric of claim
 16. 18. The flame retardant fabric of claim15, wherein the flame retardant fabric has a basis weight of from 5.5 to11 ounces per square yard.
 19. A flame retardant article of clothingcomprising the flame retardant fabric of claim 18.